Effects of Laser Irradiation on the Sublimation of BC1₃-Xe Solid Mixture

Abstract

A gaseous mixture of BCl₃ and Xe (1: 100) is injected onto a Ge substrate at 68 Kto form rare gas solid. The temperature of the solid is raised up to 72.5 K, and the solid is irradiated with chopped infrared beam from a CW CO₂ laser, 10-P (20), 944.18cm^-1, 2.5W, 110 Hz, 0.5 duty, in order to excite selectively ¹¹BCl₂ υ₃ vibration. Changes of the vacuum pressure in the system is measured with ionization gauges. The sublimation of the xenon solid is divided into two stages by the order of the vacuum pressure. The pressure is the order of 10^-4 Torr in the first stage, and is the order of 10^-5 Torr in the second stage. When ¹¹BCl₃ is being excited selectively, by cutting the laser beam, the vacuum pressure decreases 10% in the first stage, whereas in the second stage it strangely increases more than 5 %. If the laser frequency is shifted to the off resonant value of the vibration of guest molecules, 9-P (30), 1037.44cm^-1, 2.5W, no special change of pressure relating to laser irradiation is observed in the both sublimation stages. From the result of these experiments, it is likely said that in the second stage, the sublimation is suppressed by the selective excitation of the vibration of guest molecules in the xenon solid.